Figure 6.

(A) Dot blots of the fractions recovered from the sucrose gradient (27) (fractions 1–4, samples recovered from top to bottom of the sucrose gradient). The yield of protein reconstitution into PC/SM/Chol 2:1:1 and 1:1:1 vesicles was virtually the same (∼50% of SCR successfully reconstituted). (B) SCR quantification in each recovered fraction when reconstituted in PC/SM/Chol 2:1:1 vesicles (gray bars) or PC/PS 9:1 vesicles (black bars). The recovered top fraction was used for the flip-flop assay. White bars correspond to pure ultracentrifuged protein. (C and D) Influence of Chol on py-SM (C) and NBD-PS (D) transbilayer movement promoted by SCR. All measurements were made in the presence of 5 mM calcium. (Δ) Liposomes. (▲) SCR proteoliposomes of DOPC/SM/Chol 2:1:1. (▪) SCR proteoliposomes of POPC/PS/Chol 9:1:3.3. (●) SCR proteoliposomes of PC/PS 9:1. (○) SCR proteoliposomes in the absence of Ca²⁺. Average values ± SEM (n ≥ 3).